Identification of impurities and statistical classification of methamphetamine hydrochloride drugs seized in China.

A total of 48 methamphetamine hydrochloride samples from eight seizures were analyzed using gas chromatography-mass spectrometry (GC-MS) and gas chromatography with a flame ionization detector (GC-FID). Major impurities detected include 1,2-dimethyl-3-phenylaziridine, ephedrine/pseudoephedrine, 1,3-dimethyl-2-phenylnaphthalene, 1-benzyl-3-methylnaphthalene. These data are suggestive of ephedrine/pseudoephedrine as the main precursor of the methamphetamine hydrochloride samples seized during 2006-2007. Additionally the presence of 1,3-dimethyl-2-phenylnaphthalene, 1-benzyl-3-methylnaphthalene is indicative that six seizures were synthesized via the more specific ephedrine/hydriodic acid/red phosphorus method. In addition, five impurities were found for the first time in methamphetamine hydrochloride samples. Seventeen impurity peaks were selected from the GC-FID chromatograms. The peak areas of the selected peaks were then grouped for cluster analysis.